Dorian McILROY (@dmcilroy.bsky.social)

Respiratory syncytial virus infection induces heterologous protection against SARS-CoV-2 through γδ T cell-mediated trained immunity and the activation of SARS-CoV-2–reactive mucosal T cells | Journal of Virology The mechanisms by which prior respiratory viral infections confer heterologous protection remain largely undefined. In this study, we investigated whether respiratory syncytial virus (RSV) infection influences host susceptibility to subsequent SARS-CoV-2 infection in mice. We found that prior RSV exposure conferred dose- and time-dependent heterologous protection against SARS-CoV-2. Mechanistically, RSV infection induces γδ T cell-mediated trained immunity, enhances antigen-presenting cell activation, and promotes the generation of SARS-CoV-2–reactive mucosal T cells. Together, these immune responses contribute to cross-protective immunity against SARS-CoV-2. Our findings offer new insights into the immunological interplay between co-circulating respiratory viruses and SARS-CoV-2, with implications for future vaccine design and pandemic preparedness. https://journals.asm.org/doi/10.1128/jvi.01658-25